I understand you're looking for a PC download, particularly from a site called Apunkagames (which often repacks older games).
Forza Horizon 1 was never officially released for PC . It was an Xbox 360 exclusive and is currently delisted from the Microsoft Store. Official Forza Community Forums If you are looking for a "PC download" from sites like Apunka Games forza horizon 1 pc download apunkagames updated